Devices, whereby a securing of the femoral head against rotation is attempted by a single hip screw, i.e. a longitudinal bone fixing means, are already known. From EP 0 441 577, for example, a device is known that has a sleeve accommodating the hip screw in a sliding manner, while the sleeve can be secured against rotation in the intramedullary pin by a locking screw proximally introduced into the intramedullary pin. The shaft of the hip screw and the bore of the sleeve are, however, not circular, so that the hip screw cannot rotate in the sleeve. However, during the introduction into the head of the femur the hip screw has to be able to rotate. For this reason during implantation the hip screw has to be inserted first and the sliding sleeve only afterwards. There is further the danger that the hip screw moves medially when a compression screw is not additionally employed. A further disadvantage is, that the locking screw has to be introduced from above (cranially) into the intramedullary pin, representing a further operating procedure. Finally, in the case of a potential subsequent removal of the hip screw, a relatively great intervention is required to release the locking screw, screwed proximally into the intramedullary pin, in one step prior to removing the hip screw.
Furthermore, from U.S. Pat. No. 5,454,813 to Lawes, an intramedullary pin with a hip screw and a sliding sleeve is known, wherein the transition in the intramedullary pin, the external and internal profile of the sliding sleeve, and the shaft of the hip screw have a non-circular construction. Consequently, the sliding sleeve acts as an anti-rotational means between the hip screw and the intramedullary pin. This known device has the disadvantage that the prior introduced hip screw has to be rotated again one way or another during the assembly of the sliding sleeve, until it is so aligned that the non-circular cross-sections of the shaft, the external and internal profiles of the sliding sleeve and of the passage allow the introduction of the sliding sleeve. This means a time-consuming adjustment for the surgeon. A further disadvantage of this device is that a medial movement can be prevented only with an additional component (tension adjuster).
The purpose of the preceding discussion of the state-of-the-art is merely to explain the field of the invention and is not an admission that the state-of-the-art quoted has actually been published or is public knowledge at the time of this application.